The present invention generally relates to the field of gantry type cranes used for handling standardized cargo containers and more particularly it relates to the periodic inspection, painting and servicing of the large structural elements of the crane supporting frame and boom structure as recommended by the manufacturer. For example, the crane's support and boom structures must periodically be X-rayed or ultrasonically tested for evidence of structural fatigue, and must periodically be stripped, primed, and repainted.
Inspection and maintenance of large cranes is a time consuming and costly task heretofore involving the use of "skyclimbers" that repell down the crane's structural parts or the use of expensive mobile equipment, or both. Extendible boom gantry cranes, such as the PORTAINER.RTM. cranes manufactured by the Paceco subsidiary of the Fruehauf Corporation, are very large crane structures having booms supported 80 feet from the base of the crane. The time required for maintenance operators to climb, inspect and/or service such a structure is substantial with the normal safety risks attendant such working conditions. Also, the normal inspection and maintenance of the boom requires the boom to be extended in its operating position over a waterway. A boom in this position for any length of time can create a hazardous condition for ship traffic.
The present invention provides a new adjustable service platform apparatus which reduces the costs and safety risks associated with crane inspection and maintenance. The adjustable service apparatus can be stowed in a compact shippable form and, when needed, assembled easily at the dock site for use by the crane inspection and maintenance crew. In accordance with the invention the adjustable service platform can be readily engaged and lifted by conventional crane lifting hardware and can be hoisted and trollied by the crane operator and then further adjusted by the platform operator to bring the apparatus' work platforms into position next to any desired structural element of the crane support frame or boom structure. The adjustable platform apparatus provides for independant horizontal and vertical positioning of the work platform to provide, through crane and platform operator control, direct access to structural surfaces being inspected and serviced. Also, the invention provides a stable structure, the movement of which is interlocked to prevent collision with the crane support structure. Consequently, the service platform apparatus of the invention will be relatively safe to operate.
The invention is particularly adapted to be used with standardized crane lifting hardware used worldwide for securing and lifting the standardized shipping containers. The standardized hardware includes an elongated rectangularly shaped steel beam structure known in the industry as a "lifting spreader" which approximately conforms in shape and dimension to the top surface of a cargo container. The lifting spreader is suspended from the ends of the lifting ropes which in turn are suspended from the moveable trolley on the crane's gantry. The spreader lockingly engages to the top of a cargo container by means of four corner twist locks which can be operated remotely by the crane operator in the crane operator's cab. The spreader itself is attached to the ends of the lifting ropes, either through sheaves directly pinned to the top of the lifting spreader or by means of a headblock which connects to the lifting spreader. A conventional style of headblock is a quick release headblock which twist lock connects to the top of the lifting spreader and which can very easily pick up the spreader through a simple crane movement.